Carburetor anti-surge device



June 11, 1968 M. c. BROWN ET AL CARBURETOR ANTI-SURGE DEVICE Filed Oct. 23, 1965 INVENTORS MORRIS C. BROWN CHARLES L.MARTIN Md-d u 1 United States Patent 3,387,831 CARBURETOR ANTI-SURGE DEVICE Morris C. Brown and Charles L. Martin, St. Louis, Mo., assignors to ACF Industries, Incorporated, New York, N.Y., a corporation of New Jersey Filed Oct. 23, 1965, Ser. No. 503,449 7 Claims. (Cl. 261-51) ABSTRACT OF THE DISCLOSURE A carburetor having an anti-surge cylinder including a first tubular member and a thin walled second tubular member surrounding and spaced from the first tubular member to form an annular anti-surge chamber. Ports provided in the tubular members are in communication with air and fuel. A linkage connects the throttle to a metering rod which controls the flow of fuel to the antisurge cylinder.

This invention relates to a carburetor and in particular to an anti-surge device incorporated into the carburetor fuel system.

Carburetors of the type presently contemplated provide means for regulating the flow of air fuel mixture to an internal combustion engine. In normal carburetor construction the primary flow control device includes a throttle plate so mounted in the carburetor to be adjustable for varying the flow of air fuel mixture introduced to the engine intake manifold.

The carburetor is therefore normally provided with a main fuel system including a fuel bowl which is communicated with a nozzle terminating at a discharge opening in a venturi or throat. As sub-atmospheric pressure at the throat is varied, the amount of fuel drawn or aspirated through the nozzle will vary with intake manifold vacuum. Theoretically, the fuel flow is substantially proportional to engine manifold depression. However, in actuality and in particular, under certain operating circumstances, there is a substantial disparity between the relative amounts of fuel aspirated under these engine conditions.

Notably, during periods of rapid acceleration, the engine is subjected to an added load, or in the instance of an engine powered vehicle climbing a long steep grade. Under such conditions, at a slower or decreasing speed, engine manifold vacuum will decrease for a particular throttle setting. Thus, there will be an erratic withdrawal of fuel from the carburetor fuel well which will be reflected in erratic engine operation.

More specifically, fuel withdrawn in response to nozzle pressure, rather than passing to the nozzle in a smooth stream is introduced to the latter in sporadic surges. The effect of this surging on the engine will of course be the formation of an uneven stream of air fuel mixture which gives a characteristic engine bucking motion or rough operation.

The problem of fuel surging has been approached and successfully overcome to some extent by providing a fuel well or reservoir intermediate the nozzle and the carburetor fuel bowl. This well is provided with means for bleeding air into the nozzle thereby stabilizing to some degree the pressure acting on fuel in the well. Another ice approach toward overcoming fuel surge is that of providing an elongated tubular member in the well, which conducts fuel from the well directly to the nozzle. Said member is further provided with a plurality of longitudinally spaced openings such as in the manner shown in US. Patent 3,149,184, so that atmospheric air may be introduced through the respective openings and mixed with the fuel prior to the latter entering the fuel nozzle. It has been found that in spite of the above mentioned methods for overcoming fuel surge, however, the problem persists in many carburetors.

A still further generally universal problem encountered in carburetors is a propensity toward fuel evaporation particularly during hot soak or hot idle periods. This evapo-rization is prompted by excessive heating of the entire fuel system. The vapors so formed can cause vapor lock in the system or even create sufiicient pressure to force liquid fuel from the carburetor fuel bowl and acclerating well. It has been found that this overflow can be minimized by forming an expansion chamber into which fuel vapors might expand. For example, in the presently disclosed carburetor, the accelerating well is so constructed to provide a void in the upper part thereof Within which vapors may accumulate. Without such a void, during an extensive engine hot soak period fuel vaporization would soon drain both the accelerating well and the fuel bowl. Both by the evaporator process and by the excessive pressure created against the fuel surface so as to urge the latter from the carburetor nozzle.

It is therefore one object of the invention to provide an improved carburetor fuel system embodying a fuel anti-surge device. It is a further object to provide a carburetor of the type described including a main fuel system adapted to afford a smoothly metered fuel flow under all engine operating conditions. A still further object of the invention is to provide an anti-surge device in an air bled carburetor fuel system adapted to regulate air bleed to the fuel, particularly under engine overload conditions. Another object is to provide a carburetor exhibiting a high degree of fuel economy and operating efliciency.

These and other objects of the invention will be clear to those skilled in the art from the accompanying description made with reference to the drawings appended hereto.

In overcoming the above noted enumerated problems and achieving the objectives set forth herein, there is provided a novel carburetor or charge forming device adapted for attachment to a source of liquid fuel, and designed to form an air fuel mixture for introduction to an engine intake manifold. There is provided in particular a novel carburetor fuel system embodying an antisurge arrangement immersed in the accelerating fuel well.

The carburetor includes basically a body formed about a mixture conduit to which is attached a fuel bowl, the latter includes valve means for maintaining a predetermined level of fuel in the bowl. A venturi in the mixture conduit receives a stream of air and defines an area of variable pressure. A main fuel system incorporated in the carburetor includes a main nozzle having a discharge opening disposed in the venturi. An upright well in the carburetor wall forms a passage between the fuel nozzle and fuel bowl, a metering valve disposed in said passage is operable to regulate the flow of fuel from the bowl to the well. The anti-surge cylinder disposed in the well includes a first tubular member defining an inner channel having one end immersed in fuel and the other end communicated with the nozzle. A second member defines a restricted volume chamber communicated with a. source of bleed air, and with the fuel in said well.

In the drawings:

FIGURE 1 illustrates a side elevation in partial cross section of a carburetor with parts broken. away, embodying the present invention,

FIGURE 2 is a scgrnentary view on an enlarged scale of the portion of the carburetor shown in FIGURE 1, and

FIGURE 3 is a segmentary view of an alternate embodiment of the anti-surge device shown in FIGURE 2.

Although the anti-surge apparatus herein noted and described forming the principle of the invention is applicable to numerous forms of carburetors, it is presently illustrated for convenience on a single barrel unit.

Referring to FIGURE 1, the carburetor shown generally comprises a main body formed to provide a vertical mixture conduit 11 and attached fuel bowl 12. A fuel bowl cover 13 includes an air horn 14 forming an inlet to mixture conduit 11. A throttle body 16 having a central throttle bore 17 is disposed, co-axial with and in continuation of mixture conduit 11. A float controlled valve 18 is connected to a float 19 for regulating fuel flow to the fuel bowl 12 from a fuel. tank 21 by way of conduit 23 and fuel pump 24. A throttle shaft 26 extends across throttle bore 17 and carries a throttle valve 27 formed by a plate fitting closely into bore 17. A choke valve shaft 28 including a choke valve plate 29 is journalled in fuel bowl cover 13, and extends across air horn 14 to regulate the flow of air to the mixture conduit 11 during cold starts and warm-up periods. Mixture conduit 11 further includes a venturi 31 disposed at the upstream end thereof.

The carburetor fuel system comprises basically a metering jet 32 formed in the lower side of fuel bowl 12 defining a restricted orifice 33 communicating fuel bowl 12 with fuel well 34 through passage 36. A metering rod 37 having a lower tapered end 38 is carried with said end registered in orifice 33 and is reciprocably positioned by the relative position of the throttle plate, being connected to the latter by a linkage including a lever 90 pivotally supported at pin 91 and operably connected to rod 37. An elongated push rod 92 is connected to arm 93 at one end, which arm fastens to throttle shaft 26 whereby to regulate the flow of fuel leaving fuel bowl 12, in response to the engine demand.

Elongated well 34 formed in a wall of the carburetor body 10 is preferably cylindrical in shape having the lower side co-terminus with the passage 36. The upper end of well 34 is defined by an intermediate body 39 portion which is sealably carried on body 10 having a gasket 41 disposed therebetween. An annular chamber or void 35 is formed at the well 34 upper end to permit accumulation of fuel vapor during hot soak periods. Said intermediate portion 39 includes venturi 31 having an opening 22 into which is fitted elongated nozzle 42 having a nozzle opening 43 terminating in venturi 31. An air bleed arrangement in body 39 includes an opening 44 downstream of the choke valve 29 communicating with an air bleed passage 46 having a constricted portion 47 for introducing air at substantially atmospheric pressure to fuel well 34.

Following normal construction practice, the carburetor is provided with an idle fuel system which functions when throttle plate 27 is closed thereby cutting off the supply of fuel from the main fuel system. Said idle system includes a fuel idle mixing chamber 76 having an idle port 77 into said mixture conduit 11 at a point approximating the edge of said throttle plate 27 when the latter is in closed or idle position. Passage means 78 opening into idle mixing chamber 76, although not presently shown in FIGURE 1, is communicated with the fuel bowl 12 or by other means to a source of fuel.

An idle adjust screw 79 is threadably carried in a wall of the carburetor, being rotatably positioned in a well 81 which terminates at constricted nozzle 82 opening into the mixture conduit 11. Well 81 is connected by an intermediate passage 83 to idle chamber 76 wherebyan air fuel mixture is passed into the well 81 and thereafter metered into the mixture conduit 11. Thus, when the throttle plate 27 is in closed position as shown in FIG- URE l, idle air and fuel mixture drawn through passage 78 enters the idle chamber 76, and enters conduit 11 through port 77 and a portion of the idle mixture enters conduit through idle port 82.1Idle mixture screw 79 is tapered at the inner end to register in idle port 82, thereby defining a variable orifice for regulating the flow rate of idle mixture entering the mixture conduit.

Referring to FIGURE 2, anti-surge cylinder 48 in cludes a first elongated tubular first member 49 having an upper end tightly received in an aperture 52 therefore in body 39. Member 49 may be force fitted into the aper ture, threaded therein or otherwise positioned. The other end of said member 49 extends longitudinally of the fuel well 34 and terminates at the lower end thereof adjacent to the outlet of passage 36. Said first member 49 defines a relatively narrow or partially constricted inner channel 53 through which fuel may be carried from fuel well 34 up into connecting passage 54 and thence to fuel nozzle 42. Said first tubular member is shown flared slightly outward at upper end 51 to form a tight fit with the second tubular member 56.

Said second tubular member 56 is defined by a thinwalled metallic cylinder extending preferably co-axial of said first member 49 and being outwardly spaced from the walls of the latter to define an annulus or anti-surge chamber 57 extending substantially the length of antisurge cylinder 48. As shown in FIGURE 1, member 56 extends beyond the lower terminus of inner member 49 and includes port 58 for passing fuel from the well 34 upwardly into channel 53.

The volume of the anti-surge chamber or annulus 57 achieves a degree of criticality since it must be sufficiently large to hold adequate fuel to permit eflicient engine acceleration. However, said chamber 57 is likewise restricted in order that the fuel level therein might be rapidly decreased as chamber 53 becomes exhausted of fuel. The actual space between adjacent Walls of members 49 and 56 will vary with the size and capacity of a particular carburetor.

The upper end of cylinder member 56 is provided with i a laterally positioned aperture 59 for communicating annulus 57 with air bleed passage 46 for connecting the said annulus to atmosphere.

In FIGURE 3, 61 illustrates an alternate embodiment of the anti-surge cylinder shown in FIGURE 2. The embodiment shown in FIGURE 3 is substantially identical in function and in relativity of co-operative parts with that of FIGURE 2. However, one notable difference resides in the feature of the outer tube or jacket 62 spaced from the inner member 63, being fastened at the lower end to provide a fluid tight annular seal 64 with inner member 63. Thus, the lower end of inner member 63 is elongated at a constricted neck 66 such that said elongated portion is in registry with an aperture formed in the lower end of outer member 62. In effect, this embodiment of the invention illustrates an annular space 67 about inner member 63 which is substantially fluid tight with the exception of the air inlet opening 68 at the upper end of the jacket 67 and the orifice 70 providing communication with channel 74.

Referring to FIGURES 1 and 2, under normal engine operating conditions, fuel bowl 12 will be provided with a substantially constant level of liquid fuel by the action of float member 19 disposed in the fuel bowl and operably connected to inlet valve 18 for regulating fuel flow to the bowl from tank 21. Thus, the level of fuel held in well 34 will be substantially equivalent or lower than the fuel level within the bowl 12.

It should be appreciated that under normal engine operating conditions the intake manifold vacuum will vacillate within limitations. Further, such variations will be reffected in the accelerating well by the corresponding vacillation in the height of fuel. Also the fuel height in channel 53 and in annulus 57 will generally be less than the height of fuel in well 34. This is true even though well 34 and the fuel bowl be vented to the atmosphere and interconnected by passage 36 to equalize and stabilize fluid conditions in both. Since the bowl and well 34 are in constant communication through the variable orifice 33, a liquid balancing effect is maintained so long as the carburetor altitude is maintained relative horizontal. However, under certain operating engine conditions, there will be a severe demand by the engine such that fuel will be aspirated from the well at a relatively rapid rate.

Although not presently shown, metering rod 37 is connected through a suitable linkage to throttle shaft 26 such that movement of the latter will affect a corresponding reciprocable movement of rod 37 in orifice 33. Thus, as throttle valve 27 becomes more widely opened, rod 37 will be further withdrawn from orifice 33 thereby forming a progressively larger annular opening defined by the rod tapered end 38 and orifice 33.

When an added load such as an uphill grade is imposed on the engine without a compensatory increase in throttle opening to maintain engine speed, the demand of fuel at the nozzle discharge opening 43 will be greater than the flow permitted through the metering orifice 33. A further circumstance of additional fuel demand arises when the engine is suddenly accelerated such that there is a tendency to quite rapidly exhaust the entire fuel supply from inner channel 53.

In the latter instance, the level of fuel in the inner channel 53, will gradually decrease, simultaneously bled air will be introduced through bleed passage 46 and opening 44, through the lateral aperture 59, and thence through spaced openings 69, 71, and 72 as the latter becomes uncovered, thereby in effect applying atmospheric pressure to the surface of fuel held in inner channel 53 and annulus 57.

As the fuel level in the inner channel 53 drops further, bled air is introduced through both Opening 71 and 72. The process continues as the level of fuel drops below the lower opening. At this point, with channel 53 exhausted of fuel, further withdrawal will be effected through apertures 58 and 73 which fuel stream will become intermixed with air introduced through openings 69, 71 and 72 respectively. If the engine condition persists, well 34 will be rapidly exhausted of fuel and the entire flow into passage 36 and apertures 58 and 73 Will be regulated entirely by the position of the metering rod 37 in the orifice 33.

For optimum operation of the carburetor, it is of course desirable that the fuel flow through the nozzle 42 be regulated in accordance with calibration requirements of the carburetor. It is further advantageous to rapidly attain a point where the entire fuel flow through the inner channel 53 will be regulated by the relative position of the metering rod end 38 in the orifice 33.

It is seen from the foregoing description that the present anti-surge device assures smooth running operation and to a large degree trouble free operation under hot engine conditions. It is further clear that the provision of the control vacuum of fuel in the anti-surge tube assures that the carburetor will operate under optimum conditions at all engine speeds. More particularly, during periods of rapid acceleration as fuel becomes exhausted from channel 53 Without the provision of Chamber 57, fuel level in said channel would rapidly decrease. There would however, be no comparable lowering in the level of fuel in well 43. Thus, the fuel stream issuing into nozzle 43 would tend to be rich, erratic, and in general undesirable.

With the present arrangement, as the fuel level in channel 53 rapidly decreases, the level in chamber 57 will fiow closely. There will thus be a constant introduction of air to the fuel stream passing upwardly through channel 53. This consistency in fuel level in channel 53 and chamber 57 regardless of the level in well 34 in effect, the carburetor will function at peak efiiciency during the accelerating period by providing a lean, smooth air fuel mixture to nozzle 42.

It is clear from the foregoing description that certain changes and modifications may be made in the structure of the carburetor without departing from the spirit and scope of the invention.

We claim:

1. A carburetor for an internal combustion engine hav ing an intake manifold and including; a body, a mixture conduit, a fuel bowl holding a supply of fuel, a throttle valve disposed in the mixture conduit for regulating flow of air/fuel mixture passing through the latter, and a venturi positioned in said mixture conduit,

(1) a main fuel system in said carburetor including a main nozzle having a discharge opening into said venturi, a fuel well formed in said body including a passage communicated with said bowl to receive fuel from the latter, a metering valve disposed in said passage and including,

(2) an orifice and a metering rod having a metering end operably positioned in said orifice to provide a variable annular fuel opening to thereby regulate the flow of fuel through said passage,

(2') means including a linkage connecting said throttle to said metering rod,

(3) an anti-surge cylinder suspended in said fuel Well and including an elongated first tubular member defining an inner channel having one end communicated with said nozzle, and having a fuel inlet port at the other end thereof opening into said passage,

(4) a thin Walled second tubular member surrounding and spaced from at least a portion of said first tubular member and forming an annular anti-surge chamber, of said second tubular member being spaced from and coextensive with said fuel well to form an annular chamber, means including a port in said second tubular member connecting said anti-surge chamber with atmospheric air and means defining a fuel port in said second tubular member and connected to said fuel Well, said first tubular member having a plurality of longitudinally spaced apart passages communicating said anti-surge chamber with said inner channel for introducing fuel to said inner channel as the level of fuel in the latter is decreased in response to a load imposed on said internal combustion engine, which load will normally be compensated for by said metering rod being withdrawn from said orifice to meter additional fuel into said passage whereby, said first tubular member having a flared upper end fitting tightly within said second tubular member,

(5) fuel will be withdrawn from said channel and passed into said nozzle, and thereafter will be withdrawn from said anti-surge chamber and passed into said nozzle to substantially exhaust fuel from both said channel and from said annular chamber prior to the fiow of fuel to said nozzle being regulated solely by the position of said metering rod in said orifice.

2. In a carburetor as defined in claim 1, wherein said annular chamber includes means defining a first constricted orifice (47) to permit exhaustion of fuel from said annular chamber.

3. In a carburetor as defined in claim 1, wherein said anti-surge chamber (57) is communicated with said annular chamber by a second constricted orifice (59) in said second tubular member to meter air flow entering said anti-surge chamber.

4. In a carburetor as defined in claim 1, wherein said annular chamber includes means defining a constricted passage (46 and 47) communicating said annular chamher with said mixture conduit.

5. In a carburetor as defined in claim 4, wherein said constricted passage (46 and 47) terminates at said mixture conduit at a point upstream of said fuel nozzle.

6. In a carburetor as defined in claim 1, wherein said annular chamber is vented through means including a first constricted orifice (47) to permit exhaustion of fuel therefrom, and said anti-surge chamber is vented through means including a second orifice (59), means defining a passage communicating said second orifice with said mixture conduit.

7. In a carburetor as defined in claim 6, wherein said first constricted orifice is positioned upstream of said anti-surge chamber and said annular chamber to regulate the flow of air to said anti-surge chamber and to said annular chamber respectively.

References Cited UNITED STATES PATENTS 1,562,651 11/1925 Mock. 1,613,257 1/ 1927 Woolson. 2,824,727 2/1958 Brunner et al 261-78 X 3,149,184 9/1964 Szwargulski 26169 X FOREIGN PATENTS 337,934 11/1930 Great Britain.

RONALD R. WEAVER, Primary Examiner. 

